One form of microtitration unit for testing and analysing for example biological fluids has at least one container of transparent material, for accommodating a biological test reaction mixture, with an opening for introducing the mixture.
Microtitration units of that kind which are often in the form of a plate having a plurality of containers arranged in juxtaposed relationship may be used for the routine investigation of biological fluids for medicament residues. The investigation essentially extends to the presence of antibiotics and sulfonamides. For that purpose the containers are partially filled with a biological test reaction mixture which is usually made up on the basis of agar-agar nutrient media and contains test micro-organisms and a color indicator. The biological fluid to be investigated, for example milk, is pipetted on to the biological test reaction mixture in the container. The container is then possibly closed and then incubated at the optimum temperature for the test micro-organisms in an incubation cabinet or in a water bath. During the incubation operation any medicament residue in the biological fluid to be investigated diffuse out of same into the test reaction mixture and impede metabolism of the test micro-organism. If metabolism occurs, there is a change in color of the color indicator, for example from blue to yellow whereas the presence of medicament residues is indicated by the absence of a change in color.
In order to be able to detect all possible medicament residues, tests are required, with at least two different test reaction mixtures, and that requires a plurality of test operations and is accordingly time-consuming and expensive.